Research Methodology Resourceshttp://www2.hcmuaf.edu.vn/data/quoctuan/Research%20Methodology%20-%20Methods%20and%20Techniques%202004.pdfhttp://www.is.cityu.edu.hk/staff/isrobert/phd/ch3.pdfhttp://www.londoninternational.ac.uk/sites/default/files/programme_resources/lse/lse_pdf/subject_guides/sc2145_ch1-3.pdfhttp://www.bl.uk/reshelp/findhelpsubject/socsci/topbib/methsocial/methodsresearch.pdfhttp://www.elib.tic.edu.vn:8080/dspace/bitstream/123456789/13168/1/7.pdf